Scale mouse input for high-density windows

src/platform/sdl_event_converter.cc

@@ -20,7 +20,8 @@ bool ConvertSdlEvent(SDL_Window* window, const SDL_Event& source,
       destination->payload = QuitEvent{};
       return true;
     case SDL_EVENT_WINDOW_RESIZED:
-    case SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED: {
+    case SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED:
+    case SDL_EVENT_WINDOW_DISPLAY_SCALE_CHANGED: {
       WindowResizedEvent resized;
       if (!SDL_GetWindowSize(window, &resized.logical_width,
                              &resized.logical_height) ||

src/runtime/roblox_input_router.cc

@@ -32,6 +32,12 @@ RobloxInputDispatchResult Result(RobloxInputDispatchState state,
   return {state, kind, std::move(status)};
 }
 
+float ScaleToSurfacePixels(float coordinate, int32_t logical_extent,
+                           int32_t pixel_extent) {
+  return coordinate * static_cast<float>(pixel_extent) /
+         static_cast<float>(logical_extent);
+}
+
 }  // namespace
 
 AndroidKeyMapping MapSdlKeyToAndroid(uint32_t sdl_scancode) {
@@ -493,11 +499,19 @@ RobloxInputDispatchResult RobloxInputRouter::HandleMouseMotionLocked(
                   RobloxInputEventKind::kMouseMotion,
                   Unsupported("native mouse motion is unavailable"));
   }
-  mouse_x_ = event.x;
-  mouse_y_ = event.y;
-  return NativeResultLocked(sink_.mouse_move(sink_.context, event.x, event.y,
-                                             event.delta_x, event.delta_y),
-                            RobloxInputEventKind::kMouseMotion);
+  mouse_x_ = ScaleToSurfacePixels(event.x, snapshot_.viewport.logical_width,
+                                  snapshot_.viewport.pixel_width);
+  mouse_y_ = ScaleToSurfacePixels(event.y, snapshot_.viewport.logical_height,
+                                  snapshot_.viewport.pixel_height);
+  const float delta_x = ScaleToSurfacePixels(
+      event.delta_x, snapshot_.viewport.logical_width,
+      snapshot_.viewport.pixel_width);
+  const float delta_y = ScaleToSurfacePixels(
+      event.delta_y, snapshot_.viewport.logical_height,
+      snapshot_.viewport.pixel_height);
+  return NativeResultLocked(
+      sink_.mouse_move(sink_.context, mouse_x_, mouse_y_, delta_x, delta_y),
+      RobloxInputEventKind::kMouseMotion);
 }
 
 RobloxInputDispatchResult RobloxInputRouter::HandleMouseButtonLocked(
@@ -513,9 +527,11 @@ RobloxInputDispatchResult RobloxInputRouter::HandleMouseButtonLocked(
                   RobloxInputEventKind::kMouseButton,
                   Unsupported("SDL mouse button has no Android mapping"));
   }
-  mouse_x_ = event.x;
-  mouse_y_ = event.y;
-  Status status = sink_.mouse_button(sink_.context, event.x, event.y,
+  mouse_x_ = ScaleToSurfacePixels(event.x, snapshot_.viewport.logical_width,
+                                  snapshot_.viewport.pixel_width);
+  mouse_y_ = ScaleToSurfacePixels(event.y, snapshot_.viewport.logical_height,
+                                  snapshot_.viewport.pixel_height);
+  Status status = sink_.mouse_button(sink_.context, mouse_x_, mouse_y_,
                                      event.pressed, android_button);
   if (status.ok()) {
     const auto active = std::find(active_mouse_buttons_.begin(),
@@ -538,8 +554,12 @@ RobloxInputDispatchResult RobloxInputRouter::HandleMouseWheelLocked(
                   RobloxInputEventKind::kMouseWheel,
                   Unsupported("vertical native mouse wheel is unavailable"));
   }
-  mouse_x_ = std::max(0.0f, event.mouse_x);
-  mouse_y_ = std::max(0.0f, event.mouse_y);
+  mouse_x_ = ScaleToSurfacePixels(
+      std::max(0.0f, event.mouse_x), snapshot_.viewport.logical_width,
+      snapshot_.viewport.pixel_width);
+  mouse_y_ = ScaleToSurfacePixels(
+      std::max(0.0f, event.mouse_y), snapshot_.viewport.logical_height,
+      snapshot_.viewport.pixel_height);
   return NativeResultLocked(
       sink_.mouse_wheel(sink_.context, mouse_x_, mouse_y_, event.delta_y),
       RobloxInputEventKind::kMouseWheel);

tests/roblox_input_router_test.cc

@@ -204,8 +204,13 @@ TEST_F(RobloxInputRouterTest, RoutesMouseMotionButtonAndVerticalWheel) {
                   .dispatched());
 
   ASSERT_EQ(probe_.mouse_moves.size(), 1U);
-  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].delta_x, 5.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].x, 200.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].y, 160.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].delta_x, 10.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].delta_y, -6.0f);
   ASSERT_EQ(probe_.mouse_buttons.size(), 1U);
+  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].x, 200.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].y, 160.0f);
   EXPECT_EQ(probe_.mouse_buttons[0].button, 1);
   ASSERT_EQ(probe_.mouse_wheels.size(), 1U);
   EXPECT_FLOAT_EQ(probe_.mouse_wheels[0].x, 0.0f);
@@ -213,6 +218,41 @@ TEST_F(RobloxInputRouterTest, RoutesMouseMotionButtonAndVerticalWheel) {
   EXPECT_FLOAT_EQ(probe_.mouse_wheels[0].delta_y, -2.0f);
 }
 
+TEST_F(RobloxInputRouterTest,
+       ScalesMouseCoordinatesAfterDisplayScaleChange) {
+  const RobloxInputDispatchResult resize = router_.HandleEvent(
+      Event(platform::WindowResizedEvent{1000, 800, 1250, 1000}));
+  ASSERT_EQ(resize.state, RobloxInputDispatchState::kStateUpdated);
+
+  ASSERT_TRUE(router_
+                  .HandleEvent(Event(platform::MouseMotionEvent{
+                      400.0f, 240.0f, 8.0f, -4.0f, 0}))
+                  .dispatched());
+  ASSERT_TRUE(router_
+                  .HandleEvent(Event(platform::MouseButtonEvent{
+                      true, SDL_BUTTON_LEFT, 1, 300.0f, 200.0f}))
+                  .dispatched());
+  ASSERT_TRUE(router_
+                  .HandleEvent(Event(
+                      platform::MouseWheelEvent{0.0f, 2.0f, 600.0f, 400.0f}))
+                  .dispatched());
+
+  ASSERT_EQ(probe_.mouse_moves.size(), 1U);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].x, 500.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].y, 300.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].delta_x, 10.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_moves[0].delta_y, -5.0f);
+
+  ASSERT_EQ(probe_.mouse_buttons.size(), 1U);
+  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].x, 375.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].y, 250.0f);
+
+  ASSERT_EQ(probe_.mouse_wheels.size(), 1U);
+  EXPECT_FLOAT_EQ(probe_.mouse_wheels[0].x, 750.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_wheels[0].y, 500.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_wheels[0].delta_y, 2.0f);
+}
+
 TEST_F(RobloxInputRouterTest, ScalesNormalizedTouchAndKeepsStablePointerIds) {
   EXPECT_TRUE(router_
                   .HandleEvent(Event(platform::TouchEvent{
@@ -493,8 +533,8 @@ TEST_F(RobloxInputRouterTest,
 
   ASSERT_TRUE(result.dispatched());
   ASSERT_EQ(probe_.mouse_buttons.size(), 1U);
-  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].x, 321.0f);
-  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].y, 123.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].x, 642.0f);
+  EXPECT_FLOAT_EQ(probe_.mouse_buttons[0].y, 246.0f);
   EXPECT_TRUE(probe_.mouse_buttons[0].pressed);
   EXPECT_EQ(probe_.mouse_buttons[0].button, 0);
 }